Command noticed an anomaly in their Slipgate network. After sending a few scouting parties into the anomaly, none of which have returned, they are starting to fear the worst. They sent you in to investigate the anomaly and report your findings upon your return.
This time Duke is sent to some sort of a submarine base. The alien vermin has taken over a fortress by the sub base and it's your job to cleanse 'em out.
Demolition is a very gory and explosive map. The level begins with Duke cruising on into town on his bike, crashing through gates and ploughing through bad guys all in nicely explosive fashion. Almost every street building you see in the beginning is susceptible to being blown up. Even your all your weapons now have explosive properties.